Looking for a 8 to 10-day vacation idea from the east coast to europe in early Sept. We are used to travelling pretty quickly and covering a lot of ground, are active, and enjoy the walkability of the cities we travel to. Last year we had our honeymoon in Greece (Naxos, Santorini) and Italy (Rome, Amalfi, Venice). This year we are hoping to go to someplace we'd never been before such as Austria and Croatia. Would either have a good mix of relaxing beach-type places and city/culture/food, especially in fall/Sept?